[Xy-pic] Enlarging arrows and tips

[Michael Barr]

Someone wrote to this list a few weeks ago asking about enlarging tips and
arrows when using extarticle.cls for making transparencies.  I don't
believe he got a satisfactory answer, but I have successfully used the
macro 

\def\fontscale#1{%
\if#1h\relax
\font\xydashfont=xydash10 scaled \magstephalf
\font\xyatipfont=xyatip10 scaled \magstephalf
\font\xybtipfont=xybtip10 scaled \magstephalf
\font\xybsqlfont=xybsql10 scaled \magstephalf
\font\xycircfont=xycirc10 scaled \magstephalf
\else
\font\xydashfont=xydash10 scaled \magstep#1%
\font\xyatipfont=xyatip10 scaled \magstep#1%
\font\xybtipfont=xybtip10 scaled \magstep#1%
\font\xybsqlfont=xybsql10 scaled \magstep#1%
\font\xycircfont=xycirc10 scaled \magstep#1%
\fi}

to scale fonts.  After starting with 
\documentclass[17pt]{extarticle}
and loading xy, then you can execute \fontscale 3 to get xy fonts at the
same magnification.  I have tried this in conjunction with my diagxy
macros which are a front end to xy-pic, but I see no reason it wouldn't
work with native xy.  In fact, it is a good idea to use \fontscale 1 even
for ordinary 12pt tex.  And fontscale h will give you 11pt.

Michael Barr